1. Field of the Invention
The present invention relates to the field of digital image processing. More specifically, the present invention relates to a method and apparatus for enhancement of digital images.
2. Related Art
Digital cameras and scanners have become increasingly popular in recent years for generating digital images. Because of the recent decreases in cost for digital cameras and scanners, more and more photo pictures are generated, transmitted and saved in digital forms by amateur users instead of professionals. Unlike professional photos, photos produced by amateur users tend to suffer from poor image quality. These image quality problems result from under exposure, over exposure, poor lighting conditions, bad focus, inappropriate scanning processes, etc.
For the above reasons, it is important to design ways to guarantee picture quality in a way that requires the least user input and that works mainly on itself, so that even amateurs can use it. The point-and-shoot camera is a good example of a product that is designed to meet this requirement.
Digital processing methods typically focus on the picture capture stage, i.e., exposure setting, focus control, etc. The state of the art in digital camera design has been quite successful by emulating traditional analog film cameras. However, camera design can not solve all of the quality problems because picture quality is partially a psychological problem.
Digital post-processing methods have been designed that include image enhancement algorithms that improve image quality. Among recent image enhancement algorithms, a tone mapping algorithm is generally employed for adjusting the distribution of pixel values to produce better quality. The use of a tone mapping algorithm has been quite successful for satellite photos, airborne photos and medical images. For these applications, a major quality enhancement purpose is to illustrate the details of the images. However, these algorithms do not work well on consumer photos, because for consumer photos, the quality enhancement is more of a psychological problem than a mathematical problem, and detail illustration is not necessarily an important factor for quality evaluation.
Recently, some computer programs have been developed for digital image enhancement for consumer pictures. An example of a successful program that provides digital image enhancement is Photoshop, a software product manufactured by Adobe. Though Photoshop includes a large repository of processing tools, it does not offer automatic processing. Users have to choose appropriate tools and parameters for their pictures based on their own judgment. Therefore, this is not a good tool for amateur users as they cannot easily determine the proper tools to use or the proper parameters to specify.
What is needed is a method and apparatus for enhancing a digital image that produces images that are perceived to be of good image quality. In particular, a method and apparatus for enhancing a digital image is needed that produces an enhanced digital image that is perceived to be of good image quality to amateur users. Also, what is needed is a method and apparatus that meets the above needs and that is automatic. Moreover, a method and apparatus is needed for enhancing a digital image that meets the above needs and that does not require user input.